1. Field of the Invention
The present invention relates generally to a desiccant cartridge for an accumulator dehydrator or receiver/dryer for use with an automotive air-conditioning system. More specifically, the invention relates to a desiccant cartridge retention system used with an accumulator dehydrator or receiver dryer.
2. Description of Related Art
Automotive air-conditioning systems commonly use desiccants for dehydrating air and refrigerants. In an automotive air-conditioning system, a receiver/dryer device positioned between the condenser and the thermal expansion valve operates to remove moisture or contaminants from the refrigerant. In operation, the refrigerant flows through the receiver/dryer and correspondingly through the desiccant contained therein whereby the desiccant performs its intended function of removing moisture from the refrigerant. During manufacture of the receiver/dryer, the desiccant is placed and secured within the interior of the receiver/dryer.
Different methods and apparatuses for securing the desiccant within the receiver/dryer are known. Where particulate desiccants are commonly used, the desiccant is held within the receiver/dryer in a manner that allows the refrigerant to pass through the desiccant to remove moisture from the refrigerant while preventing the desiccant from escaping and contaminating the air-conditioning system. One prior art method of containing the desiccant is by placing the desiccant in a permeable bag; i.e., one that enables the refrigerant to pass through while adequately containing or capturing the desiccant. This permeable bag containing the desiccant is placed within the receiver/dryer.
One example of such a system is illustrated in U.S. Pat. No. 6,309,450 to Millen et al. Millen et al. teaches a pair of fabric adsorbent units, filled with a suitable adsorbent. The fabric adsorbent units are placed within the housing of a receiver/dryer. The adsorbent units are driven against an inner wall of the housing of the receiver/dryer when sandwiched between a movable grid and an enlarged frustroconical portion of a tubular member extending longitudinally along the center axis of the housing. During assembly, the movable grid slides over the tubular member. A plurality of downwardly extending serrations on the tubular member and a plurality of complementary upwardly extending serrations on the movable grid cooperate to form a one-way ratchet type lock that secures the moveable grid to the tubular member. Accordingly, compressing the adsorbent units between the movable grid and the frustroconical portion of the tubular member, forces them outwardly against the inner sidewalls of the housing to form a seal whereby the refrigerant passes through the adsorbent units.
Using a desiccant bag has several drawbacks. One such drawback is that the form and shape of the desiccant bag does not always conform to the canister. The desiccant should extend across the entire cross-section of the refrigerant path to prevent refrigerant bypass of the desiccant. In addition, a problem may arise with adequately sealing the permeable bag to prevent loss of the desiccant and possible contamination of the system.
Another method of containing a desiccant is to place a desiccant in a cartridge or container. Subsequently the desiccant container is placed within the receiver/dryer or accumulator during manufacture of the receiver/dryer. For example U.S. Pat. No. 5,580,451 (Tack); U.S. Pat. No. 5,522,204 (Wood); U.S. Pat. No. 5,569,316 (Flaugher et al.); and U.S. Pat. No. 5,685,087 (Flaugher et al.) illustrate the use of a container assembly uniformly filled with a suitable desiccant. The desiccant container typically fits tightly within the housing of the receiver/dryer to prevent air or refrigerant from bypassing the desiccant container and ensure flow of the refrigerant over the desiccant.
As illustrated in U.S. Pat. No. 5,580,451 to Tack, the desiccant is placed within a cup assembly including a cup having an open upper end, a closed lower end, and a centrally located tubular portion. After a suitable amount of desiccant is placed within the cup, a cap is placed in the open upper end to retain the desiccant within the cup. Both the cap and the closed lower end include a number of apertures to permit the refrigerant to enter and flow through the cup assembly. A plurality of axially spaced nibs located on the inner wall of the cup operate to secure the cap within the cup. The nibs form a number of discrete detents between adjacent nibs. Accordingly, the cap locks only at discrete positions.
Typically, the amount of desiccant contained in the cup or container is based on weight such that the amount of desiccant deposited in a cup or cartridge varies because of variation in desiccant density. Further, it is desirable to compact the desiccant to reduce the amount of movement between the individual desiccant particles. Reducing movement or agitation of the particles correspondingly reduces desiccant abrasion and breakdown of the desiccant into smaller particles that may leak into the system. Accordingly, since the cap will only lock at discrete positions, there is the possibility that the desiccant will not be adequately secured within the cup assembly or that too much pressure is placed on the cap and correspondingly the desiccant to urge the cap downward to the next or lower discrete locking point.
From the above, it can be appreciated that receiver/dryer assemblies using desiccant containers of various types are not fully optimized with regard to securing the desiccant within a desiccant container. Therefore, what is needed is a desiccant container having a cap that is simple to assemble, reduces material and manufacturing costs and readily adapts to the level of desiccant in the container while securely retaining the desiccant within the container.